1. Field of the Invention:
The invention resides in the field of devices for the controlled delivery of drugs and more particularly relates to cells for the transdermal application of drugs using electrical current.
2. Description of the Prior Art:
Controlled delivery through the skin by the use of electrical current is known in the prior art. Devices heretofore employed for such purposes include a source of current, a drug reservoir, an application electrofde communicating with the reservoir and a semi-permeable membrane positioned between the reservoir and the skin. The circuit is completed by an additional grounding electrode attached to the skin resulting in the transfer of a drug in ionic form from the reservoir, through the membrane and into and through the skin. The method is particularly advantageous for applying therapeutic substances directly to a situs of concern without intrusion into the body as a whole. Thus by use of these basic devices disclosed in, for example, U.S. Pat. Nos. 4,166,457 and 4,250,878, Jacobsen et al, showing various forms of suitable electrodes, this method allows a concentrated, regulated delivery of a selected drug.
The approach is of recognized benefit for specific medical applications and refinements in the above described apparatus such as a current control device detailed in U.S. Pat. No. 4,141,359 to the same inventor are emerging as a matter of course.
However, as known to the present inventor, this technique, designated generally as epidermal iontophoresis, is presently limited to drugs which are in the free ionic state in the reservoir. Many additional drugs are known which can be bound to an ion exchange medium or to an immobilized ligand affinity medium. These compounds may be desorbed from their carrier media directly by cations or anions generated at an electrode in communication with the drug reservoir or by ions contained in an intermediate ion reservoir between the electrode and the drug reservoir and transferred by the application of an electrical current. In contrast, therefore to those devices and their method of use known in the prior art, the present invention facilitates the employment of a much wider field of therapeutic materials than has been previously possible.